Newsgroups: rec.audio.tech
Subject: Re: Switiching room lights off causes pop in speakers
References: <[email protected]>
none  writes:

> My stereo system is on the same breaker as a couple of light switches.
> One switch operates a florescent light and the other operates an
> incandescent light. When the florescent light is switched off, I get a
> pop from the loudspeakers. The other switch has no affect.

The popping sounds from the swithches and some home applicances can
sometimes enter the hifi system. The most common ways how
those enter the system are through the power supply of poorly designed
equipments (some are more suspectable to this than other), through
poorly shielded signal cables between equipments or through current
pulses on shield wires caused by ground loops. 
 
> Also, if the cd player is on or off but plugged in, the pop occurs. If
> the level were to increase past 9 or 10 o'clock, the pop would be very
> loud.

Sounds like a shielding or ground loop problem here.

> If the cd power cord is not plugged in, but otherwise connected to the
> receiver, the pop does not occur.
> This player has a 3 wire cord. If I put an adapter plug on the cd player
> power cord that lifts the ground, the pop disappears completely.

This would to me quite clearly tell that you are expencing a problem
called "ground loop", which is a very common source of humming
noise, but sometime also switch click to get through to the system.
More information on "ground loops" and how to get rid of them at
http://www.epanorama.net/documents/groundloop/index.html

> The system components are a cd player, a receiver, and a separate
> amplifier with inputs from the receiver pre amp outputs. This popping
> situation has never occurred until yesterday; however, this particular
> arrangement of components was put in place yesterday as well. 

You changed the the equipment setup which also changed in your case 
the grounding inside your system and make the grounding problem to exist.

> Two weeks
> ago,  I had to send the cd player in for repair because it suddenly quit
> reading cd's. I got the cd player back yesterday. But, I also had to
> send my home theater pre amp in for repair because it ceased to have
> signal on the audio outputs and it quit providing power for the DVD
> player plugged into it. The pre amp had worked fine for two years. The
> system was turned off one evening, yet the next day when turned on
> again, the pre amp gave the results indicated. The pre amp is still out
> for repair, so yesterday is the first time I've had it set up in exactly
> this arrangement.
> 
> The cd player quit a few days before the pre amp. All of the components
> are powered via one of those outlet strips that has some surge
> protection built in. Until yesterday, I assumed the pre amp failure had
> more to do with my bad practice of stacking six components without any
> intermediate shelving space. The inadequate ventilation and being left
> on for extended periods would get the pre amp and dvd somewhat hot. The
> cd player sits by itself and although it's frequently left on for
> extended periods it has adequate ventilation.
> 
> Now I feel a little bit paranoid about the popping caused by the turning
> off of one light switch. The adapter plug seems to have corrected that
> problem. The heating problem I can take care of by implementing adequate
> spacing between components. But I don't know if there is a more serious
> underlying problem with the light switch that still needs addressing, or
> if this particular arrangement of components just happened to reveal
> something that's been there all the time.
> 
> Excuse me for rambling on so to describe this situation. If there are
> any further measures I need to take, I would appreciate learning what
> they are.

Take a look at http://www.epanorama.net/documents/groundloop/index.html
It will explain a lot on many audio system noise problems.

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/